The present invention relates to a liquid crystal display apparatus having an analog interface.
In a conventional liquid crystal display apparatus having an analog interface, for example, as described in the JP-A-2-245793 (Laid-Open Dec. 1, 1990), there are provided a liquid crystal panel including a liquid crystal display section, an analog-to-digital (A/D) converter circuit connected via an analog interface to an external device for converting input analog data having a plurality of signal levels into digital data, a voltage generator circuit for generating voltages having a plurality of levels according to gradation, a serial-to-parallel converter circuit for converting an input serial signal into a parallel signal, and latch means for simultaneously latching parallel outputs.
However, in the liquid crystal display apparatus of the conventional technology, since the digital data transformed from the analog data is invisible to the user, it is impossible, for example, to appropriately adjust the luminance, contrast, and color levels.
Additionally, in the apparatus of the article above, consideration has not been given to the setting of the reference voltage in the analog-to-digital conversion.
It is therefore an object of the present invention to provide a liquid crystal display apparatus in which the user can recognize the value of digital data converted from analog data and various adjustments such as the color level adjustment can be correctly accomplished.
Another object of the present invention is to provide a liquid crystal display apparatus in which the various adjustments such as the color level adjustment are automatically carried out using the values of digital data.
In some major aspects of the present invention, in a liquid crystal display apparatus having a liquid crystal display panel, an input analog display data is converted to a digital display data, a data portion is selected from the digital display data, and display status information is displayed on the display panel in the form of an overlay display data over the digital display data, so that display adjustment on the display panel is possible. The display adjustment may be automatically performed by use of a minimum value data and a maximum value data, found among the digital display data, for an automatic offset level adjustment and for an automatic gain level adjustment, respectively.
According to one aspect of the present invention, a liquid crystal display apparatus includes: a liquid crystal display section having a liquid crystal display panel; an A/D converting section for converting an input analog display data to a digital display data; means connected to the A/D converting section for selecting from the digital display data a data portion concerning a predetermined point on the display panel; a generator section connected to the selecting means for generating a display status indicator associated with the predetermined point on the display panel; and means connected to the A/D converting section and the generator section for producing a liquid crystal display data containing an overlay display data to be supplied to the liquid crystal display section, the overlay display data being a combination of the digital display data and the display status indicator.
According to another aspect of the present invention, a liquid crystal display appratus includes: a liquid crystal display section having a liquid crystal display panel; an A/D converting section for receiving an input analog display data and converting the input analog display data to a digital display data, the input analog display data having a black level and a brightest level, the A/D converting section including a black level controller for adjusting the black level of the input analog display data to generate a black level-adjusted analog display data and an A/D converter for converting the black level-adjusted analog display data to the digital display data using first reference level and a second reference level lower than the first reference level; a minimum value storing section connected to the A/D converter for storing a minimum value of the black level-adjusted analog display data; a maximum value storing section connected to the A/D converter for storing a maximum value of the black level-adjusted analog display data; an automatic offset adjusting section connected to the minimum value storing section for detecting a minimum value corresponding to the black level of the input analog display data and producing an adjusted offset level, the adjusted offset level being fed to the black level controller, whereby the black level of the input analog display data is shifted to the adjusted offset level, the adjusted offset level being such that a black level of the black level-adjusted analog display data is lower than the second reference level; and an automatic gain adjusting section connected to the maximum value storing section for detecting a maximum value corresponding to the brightest level of the input analog display data and producing an adjusted gain level, the adjusted gain level being fed as the first reference level to the A/D converter, whereby the first reference level for the A/D converter is changed to the adjusted gain level, the adjusted gain level being such that a brightest level of the input black level-adjusted analog display data is lower than the adjusted gain level, the digital display data from the A/D converting section being supplied to the liquid crystal display section panel.